Scanning probe microscope

ABSTRACT

A scanning probe microscope is provided for scanning a sample surface with a probe formed on a cantilever and detecting an interaction acting between the probe and the sample surface to measure a physical property including a surface shape of the sample. The microscope includes an arrangement for detecting torsion of the cantilever and for correcting a profile error caused by deflection of the probe and torsion of the cantilever based on the amount of torsion which is detected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/726,764, filed Dec. 26, 2012, which, in turn, is a divisional ofU.S. application Ser. No. 12/187,430, filed Aug. 7, 2008 (now U.S. Pat.No. 8,342,008), and, which application is based on and claims priorityof Japanese patent application No. 2007-327210 filed on Dec. 19, 2007,the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe control and measurement datacorrection technique which addresses adhesion of a probe to a side wallof a measured pattern in measurements using a scanning probe microscope.

2. Description of the Related Art

Scanning probe microscopes (SPM) are known as one of the techniques formeasuring a microscopic 3D shape. In this technique, a sharp-pointedprobe is brought into proximity to or contact with the surface of asample, and the measured amount of physical interaction such as anatomic force or the like being generated between the probe and thesample at this time is displayed as an image. An atomic force microscope(AFM), which is one of the SPM, is a technique in which an atomic forceacting between a probe attached to the end of a beam supported at onlyone end (leaf spring) called a cantilever and a sample, namely, acontact force between the probe and the sample is detected by the amountof flexure of the cantilever, and the sample surface is scanned whileperforming control such that the amount of flexure is kept constant, tomeasure a microscopic shape on the sample surface. The AFM is widelyused in various fields such as biology, physics, semiconductors,storages or the like as the technique allowing to measure a microscopic3D shape in an atomic order.

Especially in the fields of semiconductors and storages, patterns havebeen increasingly reduced in size every year, and thus, there is agrowing expectation for the AFM as the technique allowing to measure amicroscopic 3D shape in an atomic order.

Some methods are generally known as the AFM measuring method, and themethods are selectively used depending on a measurement purpose. Forexample, contact mode, which is most common, is a method of performingscanning with a probe continuously contacting a sample, and is mainlysuitable for measuring a flat sample.

On the other hand, in order to measure a pattern having a high aspectratio, the following measuring methods suitable for the high aspectpattern are used. One of the methods is a method called cyclic contactmode, in which a probe is vibrated at a vibration frequency near aresonance point, and scanning is performed while performing control suchthat the vibration amplitude (setpoint) of the probe at the time whenthe probe contacts a sample is kept constant. In this method, damages toa soft and brittle sample and the probe are reduced since the probeintermittently contacts the sample during probe scanning and the probedoes not continuously drag along the sample as in the contactmeasurement.

Also, a method disclosed in Japanese Patent Publication No. 3925380(Patent Document 1) can be cited as an effective measuring method inmeasuring the high aspect pattern. This method is a method of performinga measurement by completely pulling a probe away from a sample 101,moving the probe to a next measuring point, and then, bringing the probecloser to the sample again during probe scanning. Both of the abovemeasuring methods are featured by bringing the probe into intermittentcontact with the sample.

In the case of the cyclic contact mode method, the measurement isperformed with the probe dynamically contacting the sample, unlike themethod disclosed in Patent Document 1 in which the measurement isperformed with the probe statically contacting the sample. Moreover,Japanese Patent Laid-Open Publication No. 2004-132823 (Patent Document2) discloses a measuring method in which a method disclosed in JapanesePatent Laid-Open Publication No. 11-352135 (Patent Document 3) and theprobe operation disclosed in Patent Document 1 are combined (a method ofperforming a measurement by repeating retraction from and approach to asample with a probe being vibrated).

Also, Japanese Patent Laid-Open Publication No. 2006-329973 (PatentDocument 4) discloses a method of controlling all the time a retractionposition of a probe at a minimum required distance to be released fromadhesion and temporarily increasing the retraction distance when a bumpis detected, and also, an example in which a carbon nano tube is bent byan electrostatic force to accurately measure the bump. Japanese PatentLaid-Open Publication No. 07-270434 (Patent Document 5) discloses that aprobe capable of vibrating in a horizontal direction is brought intocontact with a side wall by successive taps such that the probe is notaffected by adhesion when the probe contacts the side wall of a groovein an integrated circuit. Also, a method of removing a measurement errorresulting from a probe shape is described in J. S. Villarrubia,“Algorithms for Scanned Probe Microscope Image Simulation, SurfaceReconstruction and Tip Estimation”, Journal of Research of the NationalInstitute of Standards and Technology, Volume 102, Number 4, July-August1997 (Non-Patent Document 1), and David Keller, “Reconstruction of STMand AFM images distorted by finite-size tips”, Surface Science, 253(1991) 353-364 (Non-Patent Document 2).

Among the fields in which the AFM is increasingly used, circuit patternshave been increasingly reduced in size along with circuit integration inthe field of semiconductors, and recording patterns have beenincreasingly reduced in size as recording densities have been increasedin capacity in the field of optical disks and magnetic disks (patternedmedia). It is desirable that patterns are evaluated in a developmentprocess and the results are fed back to the development process tothereby improve the efficiency of development. The size reduction of themeasured patterns (semiconductor circuit patterns, optical disk pits,bit arrays of patterned media) reaches the order of several tens of nm.Thus, when these patterns are measured by the AFM, a technique forhandling an elongated probe used for the pattern having a high aspectratio becomes important.

As a typical elongated probe, there are an Si probe whose tip issharp-pointed for the pattern having a high aspect ratio, a carbon nanotube (CNT) probe as a carbon probe, a high density carbon (HDC) probe orthe like. Among the above probes, the Si probe and the HDC probe have atip diameter of about a few nm at the smallest, but have a taperedshape, and the aspect ratio is 10 or more at the largest. On the otherhand, the CNT probe used in the AFM has a probe diameter of 10 nm ormore, but has a columnar shape, and the aspect ratio is higher.Accordingly, the CNT probe is very useful for measuring a microscopicpattern having a high aspect ratio.

However, in the case where a pattern having a steep side wall ismeasured using the elongated probe, there occurs a problem that, whenthe probe approaches the side wall of the pattern, the probe isattracted and adheres to the side wall due to the van der Waals forcesacting between the probe and the side wall. An error occurs in themeasured profile of the side wall portion due to torsion of a cantileverand deflection of probe caused by the adhesion. Furthermore, in the casewhere a pattern having a groove width almost equal to the diameter of aprobe is measured, the probe adheres to both side walls and the probecannot reach the groove bottom. Thus, the groove depth cannot bemeasured. Also, if a measurement contact force is set to be large suchthat the probe reaches the groove bottom, there occurs a new problemthat damages to the probe and the sample are increased and a profileerror increases due to slipping of the probe occurring in the steep sidewall portion of the pattern.

SUMMARY OF THE INVENTION

A scanning probe microscope according to the present invention is ascanning probe microscope for scanning a sample surface with a probeformed on a cantilever and detecting an interaction acting between theprobe and the sample surface to measure a physical property including asurface shape of the sample, comprising means for detecting adhesion ofthe probe to a side wall of a measured pattern, wherein a control stateof the probe is changed when the adhesion is detected.

Also, a scanning probe microscope according to the present invention isa scanning probe microscope for scanning a sample surface with a probeformed on a cantilever and detecting an interaction acting between theprobe and the sample surface to measure a physical property including asurface shape of the sample, comprising means for detecting a side wallportion of a measured pattern, wherein a control state of the probe ischanged when the probe reaches the side wall portion of a measuredpattern.

Also, a scanning probe microscope according to the present invention isa scanning probe microscope for scanning a sample surface with a probeformed on a cantilever and detecting an interaction acting between theprobe and the sample surface to measure a physical property including asurface shape of the sample, comprising means for detecting torsion ofthe cantilever, wherein a profile error caused by deflection of probeand torsion of the cantilever is corrected.

According to the present invention, a microscopic pattern shape having ahigh aspect ratio can be measured, and by using the present inventionfor research and development in the fields of semiconductors andstorages in which patterns will be further reduced in size in thefuture, the efficiency of research and development can be improved.Also, by applying the present technique to mass production management inthe fields, the product yield can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view illustrating an apparatus configuration ofa scanning probe microscope according to an embodiment 1 of the presentinvention;

FIG. 2 is an explanatory view illustrating the height change rate of ameasured profile at the time of measuring a pattern having a high aspectratio;

FIG. 3 is an explanatory view illustrating the height change rate of ameasured profile and torsion of a cantilever at the time when a probeadheres to a side wall;

FIG. 4 is an explanatory view illustrating slipping and adhesion of aprobe in a side wall portion;

FIG. 5 is an explanatory view illustrating the height change rate of ameasured profile and torsion of a cantilever caused by slipping andadhesion of a probe occurring in a side wall portion at the time ofmeasuring a pattern having a high aspect ratio;

FIG. 6 is an explanatory view illustrating a probe operation and achange in flexural signal at the time of measurement;

FIG. 7 is an explanatory view illustrating the amount of flexure and theamount of torsion of a cantilever when a probe slips on a side wallportion;

FIG. 8 is an explanatory view illustrating the amount of flexure and theamount of torsion of a cantilever when a probe adheres to a side wallportion;

FIG. 9 is an explanatory view illustrating a method of increasing anddecreasing a contact force between a probe and a side wall afteradhesion to a side wall is detected;

FIG. 10 is an explanatory view illustrating a method of increasing anddecreasing a contact force between a probe and a side wall afteradhesion to a side wall is detected;

FIG. 11 is an explanatory view illustrating a method of increasing acontact force using the amount of torsion of a cantilever after adhesionto a side wall is detected;

FIG. 12 is an explanatory view illustrating an apparatus configurationof a scanning probe microscope according to an embodiment 2 of thepresent invention;

FIG. 13 is an explanatory view illustrating a probe operation and achange in flexural vibration amplitude signal at the time ofmeasurement;

FIG. 14 is an explanatory view illustrating the flexural vibrationamplitude of a probe and the amount of torsion of a cantilever when aprobe slips on a side wall portion;

FIG. 15 is an explanatory view illustrating the flexural vibrationamplitude of a probe and the amount of torsion of a cantilever when aprobe adheres to a side wall portion;

FIG. 16 is an explanatory view illustrating the flexural vibrationamplitude and the torsion vibration amplitude of a probe in a flatportion and a side wall portion of a measurement sample;

FIG. 17 is an explanatory view illustrating a method of increasing anddecreasing a contact force between a probe and a side wall afteradhesion to a side wall is detected;

FIG. 18 is an explanatory view illustrating a method of increasing anddecreasing a contact force between a probe and a side wall afteradhesion to a side wall is detected;

FIGS. 19(A) and 19(B) are explanatory views illustrating one example ofa probe action in a scanning probe microscope of a cyclic contact modemethod according to an embodiment 3 of the present invention;

FIG. 20 is an explanatory view illustrating adhesion of a probe in aside wall portion according to an embodiment 4 of the present invention;

FIG. 21 is an explanatory view illustrating a measured profile and theamount of torsion of a cantilever at the time of measuring a 90-degreesidewall;

FIG. 22 is an explanatory view illustrating a method of obtainingtorsion sensitivity of a cantilever;

FIG. 23 is an explanatory view illustrating an error of a measuredprofile at the time of performing a measurement with a cylindricalprobe;

FIG. 24 is an explanatory view illustrating a method of increasing thenumber of measuring points on a side wall portion;

FIG. 25 is an explanatory view illustrating a method of increasing thenumber of measuring points on a side wall portion; and

FIG. 26 is an explanatory view illustrating deformations and a vibrationstate of a cantilever.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be describedwith reference to the drawings.

Embodiment 1

A method of measuring the depth of a groove pattern using an elongatedprobe in a step-in (registered trademark) measuring method disclosed inPatent Document 1 will be described below. First, a configurationexample of a scanning probe microscope according to the presentinvention will be described with reference to FIG. 1.

An apparatus is constituted by a coarse-movement stage 102 capable ofmoving with a measurement sample 101 placed thereon, a measurement probe103 having a probe tip on a cantilever for scanning the sample, an XYZscanning drive section 104 for driving the probe in XYZ directions, aflexure and torsion detecting section 105 for detecting flexure 2601 andtorsion 2602 as shown in FIG. 26 which are static deformations of thecantilever, a driving displacement detecting section 106 for detectingthe driving displacement of each XYZ axis, a sampling circuit 107 forsampling each sensor signal detected, a probe control section 108 forgiving an instruction to the XYZ scanning drive section 104, a generalcontrol section 109 for controlling the coarse-movement stage,measurement sequences or the like, a data storing section 110 forrecording data, an arithmetic processing section 111 for performingarithmetic processing or the like, a result displaying section 112 fordisplaying a processing result in the arithmetic processing section, anda sample 113 used in torsion sensitivity calibration of the measurementprobe 103. A piezoelectric element capable of controlling the amount ofdeformation by an applied voltage, and also, other drive elements suchas a voice coil motor or the like may be used as the XYZ scanning drivesection 104. Also, optical lever detection or the like generallycomposed of a laser and a quadrant photo detector is used in the flexureand torsion detecting section 105. In the optical lever detection, theamount of flexure 2601 and the amount of torsion 2602 of the cantileveras shown in FIG. 26 can be detected as a change in laser spot positionon the photo detector. Although the example in which the XYZ scanningdrive section 104 is arranged in the probe side is shown, arranging theXYZ scanning drive section 104 in the sample side instead of thecoarse-movement stage causes no problems in carrying out the presentinvention.

At the time of measurement, the probe is brought into proximity to orcontact with the sample surface, and while the relative positions of theprobe and the sample are scanned by the coarse-movement stage 102 or theXYZ scanning drive section 104, a physical interaction such as an atomicforce or the like occurring at this time is measured by a sensor of theflexure and torsion detecting section 105. An output signal from eachsensor is obtained at a given timing by the sampling circuit 107. Theprobe control section 108 outputs a drive signal to the XYZ scanningdrive section 104 based on the output of the flexure and torsiondetecting section 105 and the driving displacement detecting section 106to control approach and retraction of the probe to and from the sample101. When the probe reaches each measurement position, each sensorsignal is recorded in the data storing section 110 by a trigger signalfrom the probe control section 108, and is displayed as a numeric valueor an image in the result displaying section 112 through the processingin the arithmetic processing section 111. Also, at the time of measuringthe surface shape of the sample, an electrostatic capacitance orresistance can be measured by applying a voltage between the probe andthe sample in addition to mechanical properties of the sample surface.

In the following, a method of measuring a microscopic concave-convexpattern using the elongated probe will be described. In the presentinvention, when the probe adheres to a side wall of the pattern, theadhesion of the probe to the side wall is detected. A contact forcebetween the probe and the sample is increased only when the adhesion isdetected to cause the probe to reach the bottom of a concave portion ofthe pattern. First, a method of detecting the adhesion of the probe tothe side wall will be described.

Since the adhesion of the probe to the side wall is a phenomenon inwhich torsion occurs in the cantilever in the side wall portion, theadhesion can be detected from the torsion of the cantilever occurring inthe side wall portion. When the side wall portion of the pattern ismeasured by the probe, the height change rate of the measured profilesharply increases in comparison with a flat portion. Accordingly, themeasured profile can be identified as the side wall portion according tothe height change rate of the measured profile. The height change rateof the measured profile can be acquired by obtaining a difference inheight data between respective measuring points (203) as shown in FIG.2. By providing a threshold 201 in the change rate, the measured profileis determined to be the side wall portion when the change rate reachesthe threshold or more.

Furthermore, when the torsion of the cantilever is detected in ameasurement position where the height change rate increases as shown inFIG. 3, the adhesion to the side wall portion can be determined tooccur. The torsion of the cantilever can be detected by the flexure andtorsion detecting section 105. A threshold 301 is provided in the amountof change in torsional signal of the flexure and torsion detectingsection 105 to determine that the torsion of the cantilever is occurringwhen the detected amount of signal change reaches the threshold 301 ormore. That is, when the change rate of the measured profile reaches thethreshold 201 or more and the change in torsional signal reaches thethreshold 301 or more, the adhesion of the probe to the side wall isdetermined to occur. Next, a method of detecting the adhesion of theprobe to the side wall when both slipping and adhesion of the probeoccur in the side wall portion will be described. The torsion of thecantilever is a phenomenon which also occurs when the slipping of theprobe occurs in the pattern side wall portion as well as when the probeadheres to the pattern side wall.

For example, torsion in the same direction occurs in the cantilever inthe case where the probe slips on a left side wall portion and where theprobe adheres to a right side wall portion as shown in FIG. 4. Thisapplies to the case where the probe slips on the right side wall portionand where the probe adheres to the left side wall portion, too. Theslipping of the probe on the side wall portion is a phenomenon occurringwhen the contact force between the probe and the sample is high, andthus, if the contact force is increased in the state, a profile error ofthe side wall portion increases. Therefore, it is desirable to increasethe contact force only when the probe adheres to the side wall. Thecause (slipping, adhesion) of the torsion of the cantilever occurring inthe respective right and left side walls can be identified by thedirection of torsion if it is possible to detect whether the torsion ofthe cantilever occurs in the right side wall or the left side wall.Therefore, the adhesion of the probe to the side wall is detected byusing the direction of height change of the measured profile and thedirection of torsion of the cantilever.

As shown in FIG. 5, the direction of height change of the measuredprofile is negative (501) in the left side wall portion, and is positive(502) in the right side wall portion. Accordingly, the right side walland the left side wall can be discriminated from the direction of heightchange of the measured profile. Also, the slipping and the adhesion ofthe probe in the respective right and left side walls are opposite inthe direction of torsion of the cantilever, and the torsional signalsthereof are also changed in the opposite direction.

That is, as shown in FIG. 5, a change 503 in the torsional signal whenthe probe slips on the left side wall portion is positive and a change504 in the torsional signal when the probe adheres to the left side wallportion is negative, which are opposite to each other. Similarly, achange 505 in the torsional signal when the probe slips on the rightside wall portion and a change 506 in the torsional signal when theprobe adheres to the right side wall portion are also opposite to eachother. Therefore, by analyzing the sign of the height change rate of themeasured profile and the direction of torsion of the cantilever in thecase where the height change rate of the measured profile reaches thethreshold or more and the change in the torsional signal reaches thethreshold or more, only the torsion of the cantilever caused by theadhesion to the side wall can be detected.

Also, as another method of detecting the adhesion of the probe to theside wall, a method of using a flexural signal and a torsional signal ofthe cantilever which can be detected by the flexure and torsiondetecting section 105 will be described. First, a probe operation and achange in the flexural signal at the time of measurement will bedescribed with reference to FIG. 6. The flexural signal is changed whenthe probe receives a force from the sample. Thus, in the state in whichthe probe is sufficiently away from the sample (no force acts on theprobe), the flexural signal has a constant value (zero point) and is notchanged.

When the probe is approached to the sample from the state in which theprobe is completely away from the sample, the probe is attracted uponreception of an attractive force from the sample surface immediatelybefore the probe is brought into contact with the sample, and the probecontacts the sample (zone a-b). When the probe contacts the sample, theflexural signal is changed in proportion to the contact force betweenthe probe and the sample. The probe continues to be lowered until theamount by which the probe is pushed into the sample reaches a givenvalue (given contact force) (zone b-c). After the amount by which theprobe is pushed into the sample reaches a given value, the retraction ofthe probe is started. The force acting on the probe is gradually reduced(zone c-d).

When the amount by which the probe is pushed into the sample disappears,no force acts on the probe (d point). After that, the state in which theprobe adheres to the sample surface is generated. At this time, theprobe receives a force in the opposite direction from that of thecontact state with the sample. Thus, the flexure of the probe isopposite to that at the time of contacting, and the flexural signal ischanged in the opposite direction from that of the contact state. Byfurther continuing the retraction, the probe is released from theadhesion state (zone d-e). After the retraction of the probe isfinished, the probe starts to approach the sample again and the seriesof operations is repeatedly performed in each measuring point.

Next, a method of detecting the adhesion to the side wall by using theflexural signal and the torsional signal will be described withreference to FIG. 7 and FIG. 8. FIG. 7 illustrates changes in theflexure and the torsional signal when the probe slips on the side wall,and FIG. 8 illustrates changes in the flexural signal and the torsionalsignal when the probe adheres to the side wall. In the case where theprobe slips on the side wall, the torsion of the cantilever caused bythe slipping of the probe occurs after the probe contacts the sample.Therefore, as shown in FIG. 7, the torsional signal is changed after theflexural signal is changed from the zero point. On the other hand, inthe case where the probe adheres to the side wall, the probe contactsthe sample after the torsion of the cantilever caused by the adhesion ofthe probe occurs. Therefore, as shown in FIG. 8, the flexural signal ischanged after the torsional signal is changed. Accordingly, by analyzingthe flexural signal and the torsional signal before and after the probecontacts the sample, the flexure of the probe to the side wall can bedetected from the order of the signal changes.

To be more specific, a contact detection threshold 701 of a low contactforce by which the slipping of the probe does not occur is set withrespect to the flexural signal, and by determining whether the torsionalsignal exceeds a torsion determining threshold 301 at the time ofdetecting a contact (at the moment when the defection signal exceeds thethreshold), the adhesion can be detected. That is, it is possible todetermine that the torsion caused by the adhesion is occurring in thecase where the torsional signal exceeds the threshold 301 at the time ofdetecting a contact, and that the torsion is not occurring in the casewhere the torsional signal does not exceed the threshold. According tothe method, only the torsion of the cantilever caused by the adhesioncan be selectively detected. Furthermore, by combining this method withthe respective methods of detecting the adhesion described above, theadhesion can be more reliably detected.

When the adhesion of the probe to the side wall is detected by the abovemethod, the contact force between the probe and the sample is increasedto cause the probe to reach the side wall bottom portion. This methodwill be described with reference to FIG. 9 and FIG. 10. FIG. 9 and FIG.10 illustrate the flexural signal and the torsional signal at the timeof measurement. As shown in FIG. 9, after the probe contacts the sample,the probe is lowered onto the sample until the contact force between theprobe and the sample reaches a contact force target value 901 forobtaining measurement data. Two types of target values, the contactforce target value 901 for obtaining data and a contact force targetvalue 902 (contact force larger than 901) for increasing the contactforce, are provided as the contact force target value. By performingforce servocontrol by setting the target value to 902, or by loweringthe probe onto the sample at a constant speed until the contact forcereaches 902, the contact force can be increased. In the case where thecontact force is increased by the force servocontrol as in the formercase, the increasing rate of the contact force becomes smaller as thecontact force approaches the target value. However, by using the methodof the latter case, the increasing rate of the contact force is alwaysconstant (the contact force is increased at a constant rate), and it ispossible to cause the contact force to reach the target contact force ata high speed.

Also, when the contact force is increased, an increase in the contactforce more than necessary increases damages to the probe and the sample,and also causes an increase in measurement time due to an unnecessaryprobe operation. Therefore, a method of detecting the arrival of theprobe at the side wall bottom portion and controlling the increase inthe contact force to the minimum necessary will be described below. Asshown in FIG. 10, when the contact force between the probe and thesample is increased at a constant rate, the contact force increases at aconstant increasing rate (the change rate of flexure of the probe) untilthe probe starts to slip on the side wall portion (zone a-b). When thecontact force reaches a given value, the probe starts to slip on theside wall portion, and thus, the increasing rate (the change rate offlexure of the probe) of the contact force between the probe and thesample becomes smaller (zone b-c). When the probe reaches the side wallbottom portion, the probe stops slipping, and thus, the increasing rate(the change rate of flexure of the probe) of the contact force becomeslarger again to be almost equal to that before the slipping occurs (zonec-d). Accordingly, by observing the change rate of the flexural signalafter changing the contact force to 902, and detecting a change point(time c) of the change rate of flexure at the time when the probereaches the pattern bottom portion, the arrival of the probe at thepattern can be detected. However, while the probe is slipping on theside wall portion, the increasing rate of the contact force maymomentarily become larger due to a shape change of the side wallsurface, a local increase in frictional force between the probe and thesample or the like. Thus, there is a possibility that the determinationis wrong if the change in the change rate of flexure is simply detected.Therefore, pushing of the probe into the sample may be stopped bydetermining that the probe reaches the side wall bottom portion when theincreased change rate of the contact force lasts for a certain period oftime or more after the time c.

Also, by using the above method only, the probe is caused to reach theside wall bottom portion in all the cases where the adhesion of theprobe to the side wall is detected. This causes no problems in measuringthe depth of a groove. However, for example, when the side wall is notvertical but has a tapered shape, it is only necessary that the probereaches a position (b point in FIG. 11) which the probe can reach whenthe probe does not adhere to the side wall from a state (a point in FIG.11) in which the probe is tilted by the adhesion. Accordingly, bystarting to observe the amount of torsion of the cantilever at the sametime as detecting the arrival at the side wall bottom portion, andstopping the pushing of the probe into the sample in a position wherethe torsion of the cantilever caused by the adhesion disappears (theamount of torsion is zero), excessive pushing of the probe into thesample can be eliminated. Practically, at the moment when the torsionalsignal crosses the zero point (1101) during the pushing of the probeinto the sample, the pushing of the probe into the sample is stopped.

After the probe reaches the side wall bottom portion by the abovemethod, measurement data is obtained. A method of obtaining themeasurement data will be described below. In the case where themeasurement data is obtained by directly using the increased contactforce, a height error occurs due to a difference in the contact forcewith other measuring points. The height error occurring in this case isexpressed by Equation (1). By correcting the measured profile by using acorrection equation shown in Equation (2), the height error due to thedifference in the measurement contact force can be eliminated.

Δh=ΔF/k  (1)

(ΔF: the difference in the contact force before and after increasing thecontact force, k: the constant of spring of the probe, Δh: the heighterror)

h=h′−Δh  (2)

(h: the corrected height, h′: the measured height)

As another measuring method, the measurement data may be obtained afterrestoring the contact force to the same contact force as those of othermeasuring points at the time when the probe reaches the side wall bottomportion. As a method of restoring the contact force, force servocontrolmay be performed by setting the target value of the force servocontrolto the contact force target value 901 again as shown in a zone d-e inFIG. 9. Also, as shown in a zone d-e in FIG. 10, the probe may be raisedfrom the sample at a constant speed until the contact force reaches thecontact force target value 901, and after the contact force returns tothe vicinity of 901, force servocontrol may be performed by setting thetarget value to the contact force 901 as in a zone e-f. By using thelatter method as in the case of increasing the contact force, thecontact force can be restored to the original contact force at aconstant rate higher than the case of using the force servocontrol, andthe increase in measurement time caused by the change in the contactforce can be reduced.

Embodiment 2

A method of measuring the depth of a groove pattern using an elongatedprobe in a cyclic contact mode measuring method disclosed in PatentDocument 2 will be described below. First, a configuration example of ascanning probe microscope according to the present invention will bedescribed with reference to FIG. 12. An apparatus is constituted by acoarse-movement stage 102 capable of moving with a measurement sample101 placed thereon, a measurement probe 103 having a probe on acantilever for scanning the sample, an XYZ scanning drive section 104for driving the probe in XYZ directions, a flexure and torsion detectingsection 105 for detecting flexure 2601 and torsion 2602 as shown in FIG.26 which are static deformations of the cantilever, a drivingdisplacement detecting section 106 for detecting the drivingdisplacement of each XYZ axis, a probe vibrating section 114 forvibrating the probe, a vibration amplitude detecting section 115 fordetecting the vibration amplitude of the probe, a sampling circuit 107for sampling each sensor signal detected by the probe, a probe controlsection 108 for giving an instruction to the XYZ scanning drive section104, a general control section 109 for controlling the coarse-movementstage, measurement sequences or the like, a data storing section 110 forrecording data, an arithmetic processing section 111 for performingarithmetic processing or the like, a result displaying section 112 fordisplaying a processing result in the arithmetic processing section, anda sample 113 used in torsion sensitivity calibration of the measurementprobe 103. A piezoelectric element capable of controlling the amount ofdeformation by an applied voltage, and also, other drive elements suchas a voice coil motor or the like may be used as the XYZ scanning drivesection 104. In the probe, microscopic vibrations can be generated inthe probe itself or an actuator constituted by the piezoelectric elementor the like disposed at the base of the probe by a signal from the probevibrating section 114. Alternatively, the signal from the probevibrating section 114 may be superimposed on the XYZ scanning drivesection 104 and microscopic vibrations may be generated in the probedriving mechanism to thereby excite vibrations in the measurement probe103. Also, vibrations may be excited by emitting a direct vibrationexciting light to the cantilever.

Also, optical lever detection or the like generally composed of a laserand a quadrant photo detector is used in the flexure and torsiondetecting section 105. In the optical lever detection, the amount offlexure 2601 and the amount of torsion 2602 of the cantilever as shownin FIG. 26 can be detected as a change in laser spot position on thephoto detector. Although the example in which the XYZ scanning drivesection 104 is arranged in the probe side is shown, arranging the XYZscanning drive section 104 in the sample side instead of thecoarse-movement stage causes no problems in carrying out the presentinvention.

At the time of measurement, the measurement probe 103 is vibrated by theprobe vibrating section 114 and is brought into proximity to or contactwith the sample surface. While the relative positions of the probe andthe sample are scanned by the coarse-movement stage 102 or the probedrive section 104, a physical interaction such as an atomic force or thelike occurring at this time is measured by a sensor of the flexure andtorsion detecting section 105. An output signal from each sensor isobtained at a given timing by the sampling circuit 107. The probecontrol section 108 outputs a drive signal to the XYZ scanning drivesection 104 based on the output of the flexure and torsion detectingsection 105 and the driving displacement detecting section 106 tocontrol approach and retraction of the probe to and from the sample 101.When the probe reaches each measurement position, each sensor signal isrecorded in the data storing section 110 by a trigger signal from theprobe control section 108, and is displayed as a numeric value or animage in the result displaying section 112 through the processing in thearithmetic processing section 111. At the time of measuring the surfaceshape of the sample, by vibrating the probe at a high frequency, theelasticity of the sample surface can be measured from a responsethereof, or by applying a voltage between the probe and the sample, anelectrostatic capacitance or resistance can be measured.

In the following, a method of measuring a microscopic concave-convexpattern using the elongated probe will be described. First, a method ofdetecting adhesion of the probe to the side wall will be described. Themeasuring method disclosed in Patent Document 2 is a method in which theprobe vibrated in the direction of flexure by the probe vibratingsection 114 is approached to or is retracted from the sample. Althoughthe method of detecting the contact force between the probe and thesample is different from the method of Patent Document 1, the torsion ofthe probe when adhering to the side wall is the same as that occurringin the method of Patent Document 1. Therefore, it is possible to detectthe adhesion of the probe to the side wall by using the same methodsdescribed using FIG. 2, FIG. 3 and FIG. 5 in the embodiment 1.

Next, a method of detecting the adhesion of the probe to the side wallusing a flexural vibration amplitude signal and a torsional signal willbe described. The contact force between the probe and the sample in thepresent measuring method is decided by the vibration amplitude(setpoint) of a flexural vibration 2603 of the probe as shown in FIG.26. The contact force becomes larger as the flexural vibration amplitudedecays by the approach of the probe to the sample. The flexuralvibration amplitude can be detected by the vibration amplitude detectingsection 115, and as to the torsion of the cantilever, the same signal asthat in the embodiment 1 can be detected by the flexure and torsiondetecting section 105.

Here, a probe operation and a change in the flexural vibration amplitudedetected by the vibration amplitude detecting section 115 at the time ofmeasurement will be described with reference to FIG. 13. Since the probeis changed upon reception of a force from the sample, the flexuralvibration amplitude has an almost constant value (free vibrationamplitude) and is not changed in the state in which the probe issufficiently away from the sample (no force acts on the probe). When theprobe is approached to the sample from the state in which the probe iscompletely away from the sample, the probe contacts the sample surface(zone a-b).

The probe receives the force from the sample surface, the flexuralvibration amplitude decays in proportion to the contact force betweenthe probe and the sample, and the probe continues to be lowered untilthe amount by which the probe is pushed into the sample reaches a givenvalue (contact force target value) (zone b-c). After the amount by whichthe probe is pushed into the sample reaches a given value, theretraction of the probe is started. The force acting on the probe isgradually decreased, and the flexural vibration amplitude is increased(zone c-d). By further continuing the retraction, the flexural vibrationamplitude has a constant value (free vibration amplitude). After theretraction of the probe is finished, the probe starts to approach thesample again, and the series of operations is repeatedly performed ineach measuring point.

FIG. 14 illustrates changes in the vibration amplitude signal of theflexural vibration and the torsional signal when the probe slips on theside wall, and FIG. 15 illustrates changes in the vibration amplitudesignal of the flexural vibration and the torsional signal when the probeadheres to the side wall. As described in the embodiment 1, in the casewhere the probe slips on the side wall, the torsion of the cantilevercaused by the slipping of the probe occurs after the probe contacts thesample. Therefore, as shown in FIG. 14, the torsional signal is changedafter the vibration amplitude of the flexural vibration is changed fromthe free amplitude. On the other hand, in the case where the probeadheres to the side wall, the probe contacts the sample after thetorsion of the cantilever caused by the adhesion of the probe occurs.Therefore, as shown in FIG. 15, the vibration amplitude of the flexuralvibration is changed after the torsional signal is changed. Accordingly,by analyzing the flexural vibration amplitude signal and the torsionalsignal while the probe is approaching the sample, the adhesion of theprobe to the side wall can be detected from the order of the signalchanges.

To be more specific, a contact detection threshold 701 of a low contactforce by which the slipping of the probe does not occur is set withrespect to the flexural vibration amplitude signal, and by determiningwhether the torsional signal exceeds a torsion determining threshold 301at the time of detecting a contact (at the moment when the flexuralvibration amplitude signal exceeds the threshold), the adhesion can bedetected. That is, it is possible to determine that the torsion causedby the adhesion is occurring when the torsional signal exceeds thethreshold 301 at the time of detecting a contact, and that the torsionis not occurring when the torsional signal does not exceed thethreshold. According to the method, only the torsion of the cantilevercaused by the adhesion can be selectively detected. Furthermore, bycombining this method with the respective methods of detecting theadhesion of the probe described above, the adhesion of the probe can bemore reliably detected.

Also, although the method of using the torsion of the cantilever isdescribed above as the method of detecting the adhesion of the probe tothe side wall, a method of vibrating the probe in the direction offlexure and the direction of torsion by the probe vibrating section 114and detecting the adhesion by the amplitude of a torsion vibration 2604of the probe as shown in FIG. 26 will be described with reference toFIG. 16. FIG. 16 illustrates the amplitude of the flexural vibration andthe amplitude of the torsion vibration accompanying the retraction andapproach operations of the probe. The torsion vibration as well as theflexural vibration is affected when the probe is approached to thesample surface. Therefore, the torsion vibration amplitude is alsochanged (1603) along with the approach operation of the probe when theprobe is approached to a flat portion of the sample. However, when theprobe adheres to the side wall portion, the torsion vibration isaffected more strongly than the flexural vibration, and thus, is sharplychanged in comparison with the flexural signal (1602). Also, when theprobe slips on the side wall portion, the change rate of the torsionvibration becomes smaller than the change at the flat portion (1604).Therefore, a threshold 1601 is provided in the change rate of thetorsion vibration when the probe is brought closer (the change rate ofthe torsion vibration amplitude 1603 at the time of bringing the probecloser to the flat portion of the sample is set as the standard for thechange rate), and it is determined that the adhesion of the probe to theside wall is occurring in the case where the absolute value of thechange rate of the torsion vibration when the probe is brought closerexceeds the threshold.

When the adhesion of the probe to the side wall is detected by the abovemethod, the contact force between the probe and the sample is increasedto cause the probe to reach the side wall bottom portion. This methodwill be described with reference to FIG. 17 and FIG. 18 illustrating theflexural vibration amplitude signal and the torsional signal at the timeof measurement. As shown in FIG. 17, after the probe contacts thesample, the probe is lowered toward the sample until the contact forcebetween the probe and the sample reaches a contact force target value901 for obtaining measurement data. Two types of target values, thecontact force target value 901 for obtaining data and a contact forcetarget value 902 (contact force larger than 901) for increasing thecontact force, are provided as the contact force target value. Byperforming force servocontrol by setting the target value to 902, or bylowering the probe onto the sample at a constant speed until the contactforce reaches 902, the contact force can be increased.

Furthermore, in the present measuring method, the increase in thecontact force can be also controlled to the minimum necessary bydetecting the arrival of the probe at the side wall bottom portion. Asshown in FIG. 18, when the contact force between the probe and thesample is increased at a constant rate, the flexural vibration amplitudedecays at a constant change rate until the probe starts to slip on theside wall portion (zone a-b). When the contact force reaches a givenvalue, the probe starts to slip on the side wall portion, and thus, thechange rate of the flexural vibration becomes smaller (zone b-c). Whenthe probe reaches the side wall bottom portion, the probe stopsslipping, and thus, the amplitude change rate of the flexural vibrationbecomes larger again to be equal to that before the slipping occurs(zone c-d). Accordingly, by observing the amplitude change rate of theflexural vibration after changing the contact force to 902, anddetecting a change point (time c) of the amplitude change rate of theflexural vibration occurring when the probe reaches the pattern bottomportion, the arrival of the probe at the pattern can be detected.However, while the probe is slipping on the side wall portion, theamplitude change rate of the flexural vibration may momentarily becomelarger due to a shape change of the side wall surface, a local increasein frictional force between the probe and the sample, or the like. Thus,there is a possibility that the determination is wrong if the change inthe amplitude change rate of the flexural vibration is simply detected.Therefore, pushing of the probe into the sample may be stopped bydetermining that the probe reaches the side wall bottom portion when thedecay rate of the vibration amplitude of the flexural vibration lastsfor a certain period of time or more after the time c.

Also, as described in the embodiment 1, for example, when the side wallis not vertical but has a tapered shape, it is only necessary that theprobe reaches a position (b point in FIG. 11) which the probe can reachwhen the probe does not adhere to the side wall as shown in FIG. 11.Accordingly, by starting to observe the amount of torsion of thecantilever at the same time as detecting the arrival at the side wallbottom portion, and stopping the pushing of the probe into the sample ina position where the torsion of the cantilever caused by the adhesiondisappears (the amount of torsion is zero), excessive pushing of theprobe into the sample can be eliminated. Practically, at the moment whenthe torsional signal crosses the zero point (1101) during the pushing ofthe probe into the sample, the pushing of the probe into the sample maybe stopped.

However, in the method of detecting the contact force in the presentmeasuring method (in which the contact force is detected by vibratingthe probe), the vibration stops if the contact force is excessivelyincreased, and the contact force cannot be detected. Thus, in the casewhere the contact force is to be increased more than the contact forceby which the vibration of the probe stops, the method of detecting thecontact force is switched to the method described in the embodiment 1(in which the contact force is detected by using the amount of flexureof the probe), and the contact force is increased by the methoddescribed using FIG. 10. In this case, it is possible to detect thearrival of the probe at the side wall bottom portion and obtain themeasurement data by the similar method to the method described in theembodiment 1. The measurement data may be obtained by directly using theincreased contact force, or by restoring the contact force to the samecontact force as those of other measuring points at the time when theprobe reaches the side wall bottom portion as described in theembodiment 1. In the case where the former method is used, a heighterror (Equation (1)) due to a difference in the contact force with othermeasuring points is corrected by Equation (2).

Also, in the case where the latter method is used, force servocontrolmay be performed by setting the target value of the force servocontrolto the contact force target value 901 again as shown in a zone d-e inFIG. 17. Alternatively, as shown in a zone d-e in FIG. 18, the probe maybe raised from the sample at a constant speed until the contact forcereaches the contact force target value 901, and after the contact forcereturns to the vicinity of 901, force servocontrol may be performed bysetting the target value to the contact force 901 as in a zone e-f.

Embodiment 31

A method of measuring the depth of a groove pattern using an elongatedprobe in a cyclic contact mode method or a method in which the cycliccontact mode and a vibration in the direction of torsion are combined(flexural vibration plus torsion vibration) will be described below. Aconfiguration example of a scanning probe microscope according to thepresent invention is shown in FIG. 12. The descriptions of therespective sections are the same as those in the embodiment 2.

In the following, a method of measuring a microscopic concave-convexpattern using the elongated probe will be described. The cyclic contactmode method is a method in which probe scanning is performed with theprobe vibrated in the direction of flexure by the probe vibratingsection 114 dynamically contacting the sample surface. In the case wherethe probe is moved from left to right of the groove pattern, the probeadheres to the left side wall of the groove, and the tilt of the probeis increased by performing scanning with the probe being held by theside wall. The torsion of the cantilever is also gradually increased(see FIG. 19(A)). By detecting the torsion of the cantilever at thistime, the adhesion of the probe to the side wall can be detected. As tothe torsion of the cantilever, the same signal as those in theembodiments 1 and 2 can be detected by the flexure and torsion detectingsection 105.

However, since the probe is continuously moved in the scanning directionof the probe in the present measuring method, the response speed ofprobe control is slow. The torsion also occurs when the probe cannotfollow the shape change of the measured pattern (when the probe catcheson the pattern). Moreover, the torsion of the cantilever at this time isin the same direction as the torsion caused by the adhesion to the leftside wall of the groove described above (see FIG. 19(B)).

Therefore, as in the description of FIG. 3, when the amount of torsionof the probe (the torsion in the direction in which the probe tiprotates in the left direction) reaches a given value or more in the casewhere the magnitude of the height change rate of the measured profilereaches a given value or more and the sign thereof is minus (occurringduring the movement of the probe in the left side wall of the grooveportion), it is possible to determine that the torsion is caused by theadhesion of the probe to the side wall. Also, concerning the case wherethe probe is moved in the opposite direction to the above direction (thecase where the probe is moved from right to left of the groove pattern),when the amount of torsion of the probe (the torsion in the direction inwhich the probe tip rotates in the right direction) reaches a givenvalue or more in the case where the magnitude of the height change rateof the measured profile reaches a given value or more and the signthereof is plus (occurring during the movement of the probe in the rightside wall of the groove portion), it is possible to determine that theprobe adheres to the side wall. According to this method, the adhesionof the probe to the side wall can be detected by distinguishing theadhesion from the case in which the probe catches on the pattern. Also,the method described above can be also applied to the scanning method inwhich the cyclic contact mode and the vibration in the direction oftorsion are combined. When the probe adheres to the side wall in thismethod, scanning is performed with the probe being held by the side walland the torsion of the cantilever as shown in FIG. 19 occurs also inthis method. Thus, the adhesion of the probe to the side wall can bedetected by detecting the torsion of the cantilever as in the case ofthe cyclic contact mode method.

After the adhesion of the probe to the side wall is detected, thecontact force is increased. At this time, the scanning of the probe maybe stopped until the increase in the contact force is finished such thatthe probe can reliably reach the groove bottom. A method of increasingthe contact force is as described above using FIG. 17 and FIG. 18 in theembodiment 2. The detection of the arrival of the probe at the side wallbottom portion described using FIG. 18 can be also used in the presentmethod.

Also, as described in the embodiment 2, there is a limit to themagnitude of the contact force to be increased (the vibration of theprobe stops when the contact force is increased) in the present methodof detecting the contact force (in which the probe is vibrated). Thus,in the case where the contact force is to be increased greater than thelimit value, the method of detecting the contact force is switched tothe method described in the embodiment 1 (in which the contact force isdetected by using the amount of flexure of the probe), and the contactforce is increased by using the methods described using FIG. 9 and FIG.10.

In this case, it is possible to detect the arrival of the probe at theside wall bottom portion and obtain the measurement data by the similarmethod to the method described in the embodiment 1. As the measuringmethod, a measurement may be performed by directly using the increasedcontact force, or by restoring the contact force to the same contactforce as those of other measuring points at the time when the probereaches the side wall bottom portion as described in the embodiment 1.In the case where the former method is used, a height error (Equation(1)) due to a difference in the contact force with other measuringpoints is corrected by Equation (2).

Also, in the case where the latter method is used, as the method ofrestoring the contact force, force servocontrol may be performed bysetting the target value of the force servocontrol to the contact forcetarget value 901 again as shown in a zone d-e in FIG. 17. Alternatively,as shown in a zone d-e in FIG. 18, the probe may be raised from thesample at a constant speed until the contact force reaches the contactforce 901, and after the contact force returns to the vicinity of 901,force servocontrol may be performed by setting the target value to thecontact force 901 as in a zone e-f.

The method of detecting the adhesion of the probe to the side wallduring probe scanning is described in the embodiments 1 to 3. However,since the adhesion of the probe occurs in the pattern side wall portion,the contact force may be increased without detecting the torsion of thecantilever when the probe reaches the side wall portion. The methodshown in FIG. 2 in the embodiment 1 (in which the threshold is providedin the height change rate of the measured profile) is used to detect thepattern side wall portion. Also, the shape data of the measured patternmay be obtained in a first measurement to identify the side wallposition of the pattern from the obtained shape data, and the contactforce may be increased when the probe reaches the identified side wallposition in a second measurement. A method of detecting the arrival atthe side wall bottom after increasing the contact force and obtainingthe measurement data is as described in the embodiments 1, 2 and 3.

Embodiment 4

A method of measuring the width of a convex pattern using an elongatedprobe will be described below. In the present invention, in addition tothe shape data, the data of the amount of torsion of the cantilever isobtained by the flexure and torsion detecting section 105 at the time ofmeasurement, and a profile error caused by the adhesion of the probe tothe side wall is corrected by using the data of the amount of torsion.First, the profile error of the side wall portion caused by the adhesionof the probe to the side wall will be described. When the probeapproaches the side wall of the pattern, the probe is attracted to theside wall due to the van der Waals forces acting between the probe andthe side wall. The probe adheres to the pattern side wall when adistance between the probe and the side wall reaches a given distance orless. The van der Waals forces acting between the probe and the sidewall depend on a distance: X between the probe and the side wall, andthe volume of the probe facing the side wall as shown in FIG. 20. As thedistance between the probe and the side wall is smaller and the volumeof the probe facing the side wall is larger, the forces increase. Thatis, in the case where a probe diameter: D and the distance: X betweenthe probe and the side wall are constant, an adhesive force increases asan insertion distance: L of the probe into the groove or hole pattern islarger. Therefore, as shown in FIG. 21, when the distance between theprobe and the side wall is large, the adhesion to the side wall occursin the lower portion of the side wall where the volume facing the sidewall is larger. As the distance between the probe and the side wall issmaller, the adhesion to the side wall occurs in the upper portion ofthe side wall. Since the distance: X between the probe and the side wallis changed according to the movement of the probe at the time ofmeasurement, the probe adheres through the upper portion and the lowerportion of the side wall depending on the distance from the side wall.When a 90-degree sidewall is measured, the side wall is measured as atapered shape widening toward the end as shown by the measured profilein FIG. 21. It is noted that in FIG. 21, when the probe tip rotates in aclockwise direction, the torsional signal is changed in a positivedirection, whereas, when the probe tip rotates in a counter-clockwisedirection, the torsional signal is changed in a negative direction.

The above tapered shape (measurement error) is caused by the fact thattorsion of the cantilever and deflection of probe occur at the time whenthe probe adheres to the side wall to deviate the probe tip positionfrom a central axis 2102 of the measurement probe 103 (FIG. 21). In thiscase, since the probe adheres with the distance between the probe andthe side wall being larger in the side wall lower portion, the amount ofdeviation of the probe tip from the central axis 2102 is larger, and theprofile error resulting therefrom also increases. The profile error isproportional to the amount of torsion of the cantilever at the time ofmeasurement. Thus, by obtaining the relationship (correctioncoefficient: C in the following) between the amount of torsion of thecantilever and the profile error resulting therefrom in advance, theprofile error can be corrected by using Equation (3) from shape data Si′in each measuring point and data Ti of the amount of torsion of thecantilever in each measuring point.

Si=Si′−C·Ti  (3)

(Si: each corrected shape data, Si′: each shape data)

A method of obtaining the relationship (correction coefficient C)between the amount of torsion of the cantilever Ti and the profile errorEi resulting therefrom in each measuring point described above will bedescribed next. As a first method, a method of measuring a standardsample in which a the 90-degree sidewall is compensated, and obtainingthe relationship between the amount of torsion of the cantilever causedby the adhesion to the side wall and the profile error resultingtherefrom will be described. FIG. 21 illustrates the shape data and thetorsion data of the cantilever at the time of measuring the 90-degreesidewall. When the distance between the probe and the side wall reachesa given distance or less, the probe is attracted to the sample. In azone a-b, the probe is attracted to the side wall and the torsion occursin the cantilever. The probe adheres to the side wall at the time whenthe distance between the probe and the side wall reaches a givendistance or less (b point). In a zone b-c, the probe adheres to the sidewall, and the torsion disappears at the time when the probe and the sidewall are parallel to each other (c point). In a zone c-d, the torsion ofthe cantilever in the case where the probe slips on the side wallportion is shown, and the torsion in the opposite direction to that ofthe adhesion occurs. The profile error Ei occurring in the zone in whichthe probe adheres to the side wall corresponds to the amount ofdeviation 2101 of the probe tip position from the measurement probecentral axis 2102. In addition, an error Pi caused by the probe shapeoccurs as the profile error which occurs in the side wall portion. Thecorrection coefficient can be calculated by obtaining the amount oftorsion of the cantilever Ti caused by the adhesion to the side wall atthe time of measuring the 90-degree sidewall and the profile error Eicaused by the torsion of the probe at this time, and acquiring therelationship therebetween using a regression calculation such as a leastsquares method or the like.

Next, a second method of obtaining the correction coefficient will bedescribed. This method is a method in which the probe is reciprocatedwith the probe tip contacting the pattern side wall and the correctioncoefficient is obtained from the relationship between the amount oftorsion of the cantilever and the amount of displacement of the probetip at this time. As shown in FIG. 22, the probe is reciprocated towardthe side wall to obtain the relationship between the amount of movementof the probe and the amount of torsion of the cantilever at this time(the graph in FIG. 22). The graph in FIG. 22 will be described below. Inthe case where the distance between the probe and the side wall islarge, there is no interaction between the probe and the side wall andno torsion occurs in the cantilever. However, when the distance betweenthe probe and the side wall reaches a given distance or less, the probeis attracted to the side wall due to the van der Waals forces to causethe probe to adhere to the side wall and the torsion of the cantileverto occur (zone a). When the probe is further moved toward the side wallfrom the state in which the probe adheres to the side wall, the torsionof the cantilever increases in proportion to the amount of movement ofthe probe (zone b). When the probe is moved in a direction away from theside wall after the amount of torsion of the cantilever reaches a givenvalue, the torsion of the cantilever decreases. After passing throughthe point where the distance between the probe and the side wall is zero(the torsion of the cantilever is zero), the state in which the probeadheres to the side wall occurs (zone c). When the probe is furthermoved in the direction away from the side wall, the probe is releasedfrom the adhesion state to the side wall and the torsion of thecantilever disappears (zone d). The correction coefficient can beobtained by calculating the amount of torsion of the cantilever withrespect to the amount of movement of the probe (the amount ofdisplacement of the probe tip) in the state (zone b or c) in which theprobe is contacting the sample (the amount obtained by dividing theamount of torsion of the cantilever by the amount of movement of theprobe: the tilt in the zone b or c in the graph of FIG. 22) in the aboveobtained data. A pattern having a side wall angle smaller than theopening angle of the probe tip is preferable as the sample used in thepresent measurement. Accordingly, the data of the amount of torsion ofthe cantilever at the time of giving displacement to the probe tip canbe obtained even when the probe is brought into contact with anyposition on the side wall.

Next, a method of correcting the error Pi caused by the probe shapedescribed above will be described. For example, in the case of a CNTprobe (whose tip has a slight curvature and whose side face iscylindrical), it is assumed that position deviation of the probe tipcaused by the adhesion to the side wall does not occur, and when theprobe is moved along an actual pattern shape, a shape including a probeshape as shown by a dotted line in FIG. 23 can be measured. Themeasurement error caused by the probe shape can be removed by using themethods described in Non-Patent Document 1, Non-Patent Document 2 or thelike. By performing the correction in combination with the removal ofthe measurement error due to the deviation of the probe tip from thecentral axis 2102, both the measurement error caused by the positiondeviation of the probe tip and the measurement error caused by the probeshape can be removed.

Next, a method of measuring a side wall shape in detail will bedescribed. If the entire area of a pattern is measured at the samemeasurement intervals, the number of measuring points on a steep sidewall portion becomes very small. It is therefore effective to increasethe number of contact points (the number of measuring points) of theprobe with the side wall portion in order to measure the shape of theside wall in detail, and when the probe reaches the side wall portion,the interval between the measuring points is reduced to increase thenumber of contact points of the probe with the side wall (see FIG. 24).The method shown in FIG. 2 in the embodiment 1 (in which the thresholdis provided in the height change rate of the measured profile) can beused as a method of detecting the side wall portion. Alternatively, thatthe probe adheres to the side wall portion may be utilized to determinethat the probe reaches the side wall portion when the adhesion isdetected. Any of the methods described in the embodiment 1 can be usedas a method of detecting the adhesion.

Also, as another method of increasing the number of measuring points onthe side wall portion, a measurement may be performed at a given heightinterval with the probe slipping on the side wall by increasing thecontact force when the arrival of the probe at the side wall is detectedby the above method. When the probe is caused to slip, it is notpossible to obtain the data of the entire surface of the side wallunless the probe adheres to the upper portion of the side wall. In thecase where the tilt of the side wall is downward with respect to ameasurement direction as shown in a zone a in FIG. 25, the probe adheresto the upper portion of the side wall first and adheres to the lowerportion of the side wall at the end. Accordingly, the state in which theadhesion is detected in the side wall portion first is the state inwhich the probe adheres to the upper portion of the side wall, and themeasurement may be performed at a given height pitch 2501 while causingthe probe to slip by increasing the contact force at this moment.However, in the case where the tilt of the side wall is upward withrespect to a measurement direction as shown in a zone b in FIG. 25, theprobe adheres to the lower portion of the side wall first and adheres tothe upper portion of the side wall at the end. Therefore, it becomesnecessary to detect the state in which the probe adheres to the upperportion of the side wall. As the probe approaches the side wall, theprobe adheres to the upper portion of the side wall and the amount ofdeviation of the probe tip position from the central axis 2102 of themeasurement probe at the time of obtaining data is gradually smaller.Furthermore, when the amount of deviation 2502 of the probe tip positionfrom the central axis 2102 is smaller than a measuring point interval2503, a next measuring point is out of the side wall and this state isthe state in which the probe adheres to the upper portion of the sidewall. Accordingly, the state in which the probe adheres to the upperportion of the side wall is detected by comparing the amount of torsionof the cantilever and the measuring point interval, and the measurementmay be performed at the given height pitch 2501 while causing the probeto slip by increasing the contact force. Any of the methods described inthe embodiment 1 may be used as a method of detecting the torsion of thecantilever used herein, and the methods described in the embodiment 1may be also used as a method of increasing the contact force.

Furthermore, the width of the convex portion can be measured byobtaining the right and left side wall shapes of the convex pattern byusing the above correction method. Although the method of correcting theshape in the convex pattern is described in the present embodiment, thepresent invention is not limited to the convex shape, and it is obviousthat the present invention can be also applied to a concave shape.

A microscopic pattern shape having a high aspect ratio can be measured,and by using the present invention for research and development in thefields of semiconductors and storages in which patterns will be furtherreduced in size in the future, the efficiency of research anddevelopment can be improved. Also, by applying the present technique tocommercial production management in the fields, the product yield can beimproved.

What we claim is:
 1. A scanning probe microscope for scanning a samplesurface with a probe formed on a cantilever and detecting an interactionacting between the probe and the sample surface to measure a physicalproperty including a surface shape of the sample, comprising means fordetecting torsion of the cantilever and for correcting a profile errorcaused by deflection of the probe and torsion of the cantilever based onthe amount of torsion which is detected.
 2. The scanning probemicroscope according to claim 1, wherein said means corrects the profileerror is corrected by obtaining a relationship between an amount oftorsion of the cantilever and the profile error from a measured profileof the sample whose side wall shape is known.
 3. The scanning probemicroscope according to claim 1, further comprising a side wall shape ofthe sample is known.
 4. The scanning probe microscope according to claim1, wherein said means corrects the profile error by obtaining arelationship between an amount of torsion of the cantilever and theprofile error from a relationship between an amount of displacement in ahorizontal direction of a tip of the probe and the amount of torsion ofthe cantilever when displacement in a horizontal direction is caused tooccur in the tip of the probe.
 5. The scanning probe microscopeaccording to claim 1, further comprising means for correcting a profileerror caused by a probe tip.
 6. The scanning probe microscope accordingto claim 1, further comprising means for detecting a side wall portionof a measured pattern, wherein measuring point pitch in a horizontaldirection is reduced when the probe reaches the side wall.
 7. Thescanning probe microscope according to claim 6, further comprising meansfor detecting the measured pattern side wall portion by analyzing amagnitude of a height change rate of a measured profile.
 8. The scanningprobe microscope according to claim 6, further comprising means fordetecting the measured pattern side wall portion by detecting adhesionof the probe to the measured pattern side wall.
 9. The scanning probemicroscope according to claim 1, further comprising means for detectinga side wall portion of a measured pattern based on a control state ofthe probe being changed when the probe reaches the side wall portion ofa measured pattern.
 10. The scanning probe microscope according to claim9, further comprising means for deleting the measured pattern side wallportion by analyzing a magnitude of a height change rate of a measuredprofile.
 11. The scanning probe microscope according to claim 9, furthercomprising means for detecting the measured pattern side wall portion bydetecting adhesion of the probe to the measured pattern side wall. 12.The scanning probe microscope according to claim 9, further comprisingmeans for changing the control state of the probe by increasing acontact force between the probe and the sample.
 13. The scanning probemicroscope according to claim 12, wherein a measurement is performed ata given height pitch during movement of the probe on the side wall bythe increase in the contact force.